It is believed that known exhaust gas recirculation (EGR) systems include a valve connected to an actuator for controlling exhaust gas flow though the EGR systems. It is believed that these know EGR systems have a number of disadvantages including constantly energizing the actuator to maintain a current level associated with holding the valve in various states, and internal heat build-up caused by being constantly energized. It is believed that another disadvantage of these known EGR systems is the absence of a fail safe provision or the need for an H-bridge. However, it is believed that H-bridges typically do not provide the necessary speed desired for fail safe operation. Finally, it is believed that the known systems are too complex and therefore less reliable.
Thus, it is believed that there is a need for a simple EGR system including a fail safe provision.
The present invention provides a system for recirculating a flow of exhaust gases. The system comprises a passage through which the exhaust gas flow passes, a valve movable in the passage between a generally open configuration and a generally closed configuration, an actuator operatively connected to the valve, and a fail-safe returning the valve to one of the generally open and generally closed configurations if the actuator is disabled. The generally open configuration of the valve substantially permits the exhaust gas flow to pass through the passage, and the generally closed configuration of the valve substantially prevents the exhaust gas flow from passing through the passage. The actuator includes a one-way driver and a release to move the valve between the generally open and generally closed configurations and to vary the exhaust gas flow though the passage.
The present invention also provides a method for recirculating a flow of exhaust gas through a passage. A valve is disposed in the passage and is movable by an actuator between a generally open configuration and a generally closed configuration. The generally open configuration of the valve substantially permits the exhaust gas flow to pass through the passage, and the generally closed configuration of the valve substantially preventing the exhaust gas flow to pass through the passage. The method comprises energizing the actuator with a power supply, and moving the valve to a fail-safe position if the power supply fails. The actuator includes a one-way driver and a release. The one-way driver moves the valve toward a first one of the open and closed configurations, and the release allows the valve to be moved toward a second one of the open and closed configurations. The energizing the actuator varies the exhaust gas flow through the valve. And the fail-safe position permits a fail-safe flow of the exhaust gas flow to pass through the passage.